Windows, when using a form of transparency, when they add the blur effect they do not blend the colors correctly. Xorg blends using the typical rule of adding the gamma together and dividing by two. The correct way is to square the gamma, add, divide by two then square root it. This results in a blurring effect that is much more pleasing to the eye and could overall improve the quality of this app.
Compiz bugs are tracked at https://launchpad.net/compiz, not here.